I don't have that book. What you propose will work fine; as long as you have access to the riser attachment to the bench work for future "adjustment" of the riser (if needed). I normally glue my risers to the sub-roadbed (and chisel it loose if needed).
I purchased Wescott's book on Benchwork also. I have been screwing the sub-roadbed from both directions from bottom up and from top down.
The only problem I can think of is once you cover the screws there's no way to go back and make any adjustments. However, at this point the sub-roadbed should be in it's final resting place ready for roadbed and track.
I'm using 1/2" plywood and using cut 1" x 2" into 1" x 1" (actually 3/4" x 3/4"). The problem I'm having is when going from the bottom up sometimes I get the point of the screw poking through. I'm using 1 1/4" sheetrock screws and screwing them at an angle so they don't go through but some still crack the surface.
Going from the top down I don't have that problem.
I don't see why screwing from top down should make any real difference. I'll probably use that technique for most of the rest of my layout since it's easier.
Bill
Bill54 wrote:I'm using 1/2" plywood and using cut 1" x 2" into 1" x 1" (actually 3/4" x 3/4"). The problem I'm having is when going from the bottom up sometimes I get the point of the screw poking through. I'm using 1 1/4" sheetrock screws and screwing them at an angle so they don't go through but some still crack the surface.
This is my process exactly and, indeed, works well. However, now that I've started, there are clearly some places that are going to be a real b---- to get at from under the benchwork. I am just trying to get a feel for what I am compromising by inserting the screws from the top of the subroadbed. Also, I notice a discrepancy in the Westcott book in that some figures depict screwing the cleat to the riser and some figures show screwing the riser to the cleat. I'm not sure if there is a "right" way to do this either. Thanks Bill54.
The sole reason he advocated coming from the bottom, was to be able to access the screws in the future if needed.
From the top, they'll be covered by the layout, thus inaccessible. If that's not a concern, carry on :)
Westcott's primary idea is that it should be possible to completely re-engineer and rebuild the "subterranean" support structure without having any effect on the finished, fully sceniced surface. Having to excavate for screws inserted from the top defeats the entire concept.
My own substructure is steel - specifically, steel stud material. My risers are short lengths of steel stud, formed at the top as necessary to provide screwing flanges on which to rest the cookie-cut plywood subgrade. All of my screws have been driven from below, many of them with the aid of a LONG cross-point bit driven either by a power drill or by a multi-bit ratchet screwdriver with a matching hex fitting at the business end. The length of the shaft gets my hands down below most of the interference. All that is needed is a more or less vertical approach to the screw being driven (or an appropriately angled approach if driving screws on a slant.)
Nice thing about using steel stud material for risers is that one riser can support "cut cookies" at several levels. All it takes is some thought, and creativeness with tin snips and bending pliers. Then all you have to do is pre-drill the screw holes.
Chuck (modeling Central Japan in September, 1964)
I don't have the book you described, but I remember the L-girder benchwork articles in MR from waaaay back.
I recall that MR ultimately concluded that the post-scenery accessibility of the screws didn't justify the extra work of adding a T piece at the top of the riser to facilitate a bottom-driven screw. I agree. If I needed to make a later adjustment I'd cut through a top-down screw with a hack-saw blade, or possibly just unfasten the riser at the gridwork and break it off.
mrnimble wrote:At the end of the day all the screw heads are going to be coverd up by roadbed, ballast or other scenery material.
That's the reason. If you ever want to adjust, rebuild, disassemble or otherwise change something, you will find it difficult.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
hardcoalcase wrote: I recall that MR ultimately concluded that the post-scenery accessibility of the screws didn't justify the extra work of adding a T piece at the top of the riser to facilitate a bottom-driven screw. I agree. If I needed to make a later adjustment I'd cut through a top-down screw with a hack-saw blade, or possibly just unfasten the riser at the gridwork and break it off.
Since Linn Westcott was working in wood, adding the screwing flange to the riser required either more screws, careful gluing or both. Later somebody came up with the idea of using white glue to make the top riser joint - screws down from the top, removed after the glue set up. In case of need, the glue joint could be broken.
This is where my steel risers shine! Due to the basic shape of the steel stud material, a screwing flange has to be bent into it no matter which way the screws are driven - and only takes a few seconds with tin snips and bending pliers. It's actually easier to drive screws up from the bottom, into pilot holes drilled down from the top (Which is how I locate the screw holes in the flanges. Mechanical pencil lead down through the pilot holes.)
Chuck (modeling Central Japan in September, 1964 - with steel stud benchwork)
When I started my 2nd layout, I was using drywall screws fastened from the top. When I had to dismantle the layout, it was a bear trying to find them to remove them. When I started the next layout, using a lot of the original layout, I used 1x1 trim cut into 3" lengths. I predrilled them (to keep from splitting) and countersunk the holes. This allowed me to use 1" wood screws. Enough of the screw went into the subroadbed to hold it firmly, but also allowed me to remove the screws afterwards without having to hunt for them, as was the case when screwed in from the top. I used 1x2s for the risers which were screwed into the benchwork, allowing me to adjust the height rather easily. This was important when making a grade from base height to 7 inches. In making the grade, I used double layers of 1/2" plywood. This gave it extra rigidity, although 3/4" would suffice, and probably be cheaper. Remember, NO LAYOUT IS EVER DONE, and anything you do to make redesigning easier will pay off in the long run.
Marlon
See pictures of the Clinton-Golden Valley RR
There is another reason for putting the screws up through the bottom. If you're nailing the track to the subroadbed, as I have done, you run the possibility of putting a nail into a screw head if the screws are inserted in through the top. I only run the screws through the top where there is no possibility of any nailing from the top for track, scenery or structure bases.
I agree with you Medina 1128, the cleats have to be pre-drilled to prevent splitting of the cleats. Countersinking the holes not only eliminates splitting of the cleats but gets shorter screws up through a 3/4" or even 1/2" plywood with a good "bite" and still not go through the subroadbed.